hnf1b genes in zebrafish hindbrain development.
The Hnf1b transcription factor acts during formation of rhombomeres (r) 5 and 6 in the hindbrain. To determine if hnf1b is absolutely required in r5/r6, we examined the hnf1b(hi2169) and hnf1b(hi1843) retroviral insertion alleles. Hnf1b(hi2169) shows highly variable residual expression of several genes in r5/r6, but this is not due to full-length hnf1b transcripts persisting in hnf1b(hi2169) embryos, nor to hnf1bl, a novel hnf1 family member expressed in r5 that we identified. Instead, we find evidence for a virus-hnf1b fusion transcript in hnf1b(hi2169) embryos and demonstrate that morpholino-mediated knockdown of this transcript leads to near-undetectable r5 gene expression. The hnf1b(hi1843) allele has a more severe phenotype with near-undetectable expression of r5/r6 genes. We next examined if hoxb1b, which functions upstream of hnf1b in r5/r6 formation, can induce expression of r5/r6 genes in hnf1b mutants. We find that microinjected hoxb1b mRNA induces ectopic gene expression anterior to the hindbrain in hnf1b(hi2169) and hnf1b(hi1843) embryos, but cannot restore gene expression in r5/r6 of the mutants. We conclude that hnf1b(hi2169) is hypomorphic to hnf1b(hi1843) and that, while hnf1b is required for r5/r6 gene expression in the hindbrain, r5/r6 gene expression can be experimentally induced independently of hnf1b anterior to the hindbrain.
Choe
Seong-Kyu
SK
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605-2324, USA.
Hirsch
Nicolas
N
Zhang
Xiaolan
X
Sagerström
Charles G
CG
D000818:Animals; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D051539:Hepatocyte Nuclear Factor 1-beta / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010802:Phylogeny; D012249:Rhombencephalon / Q000196:embryology* / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
D029961:Zebrafish Proteins; C496498:hnf1ba protein, zebrafish; D051539:Hepatocyte Nuclear Factor 1-beta